Electrical nerve stimulation device

ABSTRACT

The electrical nerve stimulation unit in accordance with the present invention generally includes a housing, an input panel, a display panel, a controller, a first channel output, a second channel output, and a power system. While the device is generally described in terms of use as a TENS unit, it must be noted that other nerve stimulation applications for the device are envisioned as well. The myriad of intelligent and proactive programmable software functions and features of the present invention are executed on the controller&#39;s microprocessor. For instance, open lead monitoring, soft recovery implementation, compliance monitoring, and enhanced power management are all controlled and monitored through the interfacing of the processor with the various devices and hardware on the unit&#39;s hardware platform.

RELATED APPLICATIONS

This application is a division of application Ser. No. 10/273,392 filedOct. 17, 2002, which claims the benefit of U.S. Provisional ApplicationNo. 60/330,116, filed Oct. 17, 2001, each of which is hereby fullyincorporated herein by reference.

FIELD OF THE INVENTION

The invention generally relates to electrotherapy devices used tostimulate the human body. More particularly, the present inventionincludes improved systems and methods for transcutaneous electricalnerve stimulation (TENS) including compliance monitoring, soft recoveryoperations, and software controlled power management.

BACKGROUND OF THE INVENTION

Clinical electrotherapy devices are used to implement many differenttypes of human medical therapy protocols. Electrotherapy devices may beused to stimulate nerves in the human body to a large number oftherapeutic ends. In addition, electrical impulses cause muscles tocontract and may be used for various forms of exercise and painmanagement.

TENS and microcurrent electrotherapy stimulation have been usedsuccessfully for the symptomatic relief and management of chronicintractable pain for many years. In general, TENS or micro currentelectrical nerve stimulation controls pain of peripheral origin byproviding a counter stimulation that interferes with the painfulsensations. While the mechanism of action of TENS is not fullyunderstood, there are several theories as to how TENS helps to relievepain. At the simplest level, stimulating peripheral nerves producespleasant sensations that assist in distracting the patient from the painsensation. This distraction is far from trivial and is often advanced asa universal method of pain relief focusing on both the conscious leveland subconscious level.

One theory argues that the relief from pain is at least partly based onthe knowledge that nerve transmissions carried by large nerve fiberstravel more quickly than nerve transmissions carried by small nervefibers. Under this theory, the electrical stimulations to large nervefibers created by the TENS unit travel to the brain more quickly, andare more powerful, than pain impulses carried by smaller nerve fibers.Thus, the electrical impulses arrive at the brain sooner than the painnerve impulses and the sensation of the large nerves overrides andblocks out the sensations from the smaller pain nerves.

Melzack and Walls proposed a working hypothesis of how TENS interfereswith pain in 1965. Melzack and Walls proposed that TENS generates anartificial abnormal noise on the nerves to enervate the skin that sharesthe same nerve roots with the pain fibers conducting the real painimpulses. When the spinal cord receives the barrage of signals from thesame region of the body, a neurological circuit turns off and stopsrelaying the pain impulses to the brain.

Another theory as to the mechanism of action of TENS is based on theunderstanding that serotonin and other chemical neurotransmittersparticipate in the pain and the pain reduction process. Under thistheory, the electrical nerve stimulation caused by the TENS unitencourages the production of endorphins which then modulate the painresponse. Alternately, the electrical stimulations in some way interferewith the production of serotonin which is involved in the pain response.

As a result of the increased understanding and studies surrounding theuse of TENS in eliminating or minimizing patient pain, many attemptshave been made to more efficiently and effectively implement TENS units.Compliance monitoring, power management, safety and comfortmaximization, simplified unit designs, and a myriad of other techniquesand methods have been advanced and modified with this increased use ofTENS in mind.

Patient compliance with treatment is a medical concern regardless of theform of treatment being applied. Compliance refers to whether thepatient is following through with the treatment as prescribed, whetherthe patient may be avoiding the treatment all together, or whether thepatient is in some way applying the treatment in a manner that is not ina form the doctor prescribed and desired. If patients are non-compliant,it becomes very difficult to determine the effectiveness of treatment,as patients are often unwilling to admit they are non-compliant. Inaddition, some forms of electrotherapy treatment may cause discomfort inwhich case the patient may have a motivation to avoid the treatmentdespite its therapeutic benefit. Even further, non-compliance concernscan limit the potential for this treatment technique since misuse willlikely weaken the economic and therapeutic draw for health careproviders and insurance companies.

As a result of this necessity to implement a level of compliance, somecurrent electrotherapy devices include compliance monitoring protocols.Generally, conventional compliance monitoring protocols include somemeans of recording the length of time for which the electrotherapydevice has been utilized in the period since the doctor has prescribedits use. Conventional compliance monitors only record when the unit ison or off during a given time period. This leaves open the possibilityof erroneously monitoring non-compliant use, since the patient may turnon the unit while it is not being utilized for therapeutic use, or theunit may be improperly connected during the power-on period. With regardto improper connections of the unit to the patient, the unit canmistakenly acknowledge therapeutic use during a period of use having nobeneficial therapeutic effects on the patient. This leads to greatuncertainty as to the effectiveness of the prescribed therapy, whetherthe current level of treatment is appropriate, or if it is in need ofadjustment or discontinuation. Since electrotherapy is generally appliedin non-constant electrical pulses, compliance monitoring becomes evenmore difficult. In general, the present art makes it necessary tomaintain voltage during the periods of time in which electrical pulsesare not being applied to the patient.

In the past, some compliance monitors have utilized transformers as partof the compliance monitoring circuitry in order to maintain voltagebetween timing impulses. Due to the physical electrical characteristicsof transformers, they are difficult to miniaturize. This contributes tobulkier electrotherapy units. The preferred mode for the application ofelectrotherapy treatment is one where the treatment can be applied forextended periods of time. This protocol is most easily applied with aunit that can be worn on the body. This allows the treatment to beapplied over a long period of time while the patient is involved innormal daily activities. If a unit is to be worn on the body for anextended period of time, a smaller unit is much preferred.

As stated, power management is an important hurdle to overcome inproviding effective TENS treatment. The use of portable units capable ofattachment to the human body requires battery operation. To promotetreatment efficacy and to lower treatment costs, it is necessary to keepthe TENS unit circuitry properly powered throughout the duration of thetreatment, and to ensure that the patient or health care professionalswill not need to replace batteries frequently, or at inopportune times.Conventional techniques to address such power management concerns haveleft room for measurable improvement. For instance, one technique hasbeen to monitor the voltage level at the battery and to initiate aresulting warning system, such as an LED flash or display panelnotification, upon determination by the device that the power hasreached a point somewhere below a desired threshold. This system isobviously flawed since it fails to in any way conserve power, or modifyperformance in an attempt to lengthen the usable life of the batterysource, and the resulting treatment period.

Another technique has been to monitor battery power for TENS units bysetting a predefined ideal power level, frequently monitoring theoverall power level, and making adjustments to power usage once theoverall power level of the battery source has reached a level below theideal power level. While this method does accommodate for lower power,it does so too late, using a power conservation plan that may prove todiminish treatment efficacy. First, power conservation and management isnot approached until power has reached a dangerously low level. Second,this critical period of low battery power is dealt with by reducingoutput power for the TENS unit, which can be obviously undesirable if itnegatively effects the proper therapeutic functioning of the unit on thepatient.

Conventional attempts at controlling the output signal of the TENS unitto patients following disruptions, defective operations, or operatormisuse have also proven problematic as they often fail to properlyprotect the patient, and the unit itself, from resulting surges. Thissurge phenomena often occurs when a lead connecting the TENS probe tothe patient is disconnected from the main unit and reconnected while thepatient is using the device. The natural reaction of the user or patientis to simply reconnect the lead and resume treatment. However,reconnection of the lead can result in a significant jump in poweroutput—from zero to the treatment level. This jump in output signal isvirtually instantaneous. As a result, such a quick spike or disruptioncan damage the unit and, more importantly, cause discomfort to, or eveninjure, the patient.

One attempt at dealing with the potential harm brought about by thesedisruptions, has been to provide for monitoring circuitry and/orsoftware within the TENS unit to quickly detect the occurrence of such adisruption. Once the disruption has been detected, the unit quicklyramps down the output signal to approximately zero. At this point ofreset, some units will await power approval and adjustment by theuser/patient before treatment and power output will be resumed atdefined levels. Other prior art teaches immediately ramping up theoutput signal to pre-disruption levels. Each of these approaches, whilean improvement, can be improved upon.

Conventional approaches are directed to accommodation and output signalmodification only after a surge has been detected. As a result, thepatient and the TENS unit experience at least a momentary spike in theoutput signal, i.e., a surge upon reconnect of a disengaged lead to theunit. While continuous power surging is not permitted, it is stillpossible that the patient will be subjected to a period of physicaldiscomfort.

Consequently, there is a need for a TENS unit that substantiallyovercomes the deficiencies and problems innately present withconventional systems and methods for compliance monitoring, powermanagement, and disruption recovery, and the like.

SUMMARY OF THE INVENTION

The present invention substantially solves the problems withconventional devices by providing a portable TENS unit capable ofmonitoring true treatment compliance, employing a system of powermanagement that significantly extends the usable life of the batterysource, and that implements a soft recovery system that substantiallyeliminates potential damage to the patient or the unit in thosecircumstances when an output signal disruption occurs.

The electrical nerve stimulation unit in accordance with the presentinvention generally includes a housing, an input panel, a display panel,a controller, a first channel output, a second channel output, and apower system. While the device is generally described in terms of use asa TENS unit, it must be noted that other nerve stimulation applicationsfor the device are envisioned as well. The myriad of intelligent andproactive programmable software functions and features of the presentinvention are executed on the controller's microprocessor. For instance,open lead monitoring, soft recovery implementation, compliancemonitoring, and enhanced power management are all controlled andmonitored through the interfacing of the processor with the variousdevices and hardware on the unit's hardware platform.

The present invention includes a compliance monitoring system for usewith miniaturized TENS units that is microprocessor controlled such thatit is less bulky than transformer-based compliance monitoring systemsknown in the prior art. The compliance monitoring system includesparameter storage that can provide a mechanism for storing a pluralityof non-volatile parameters, including modality, mode, rate, width,cycle, span and timer values. The compliance managing is preferablystored in non-volatile memory, such as EEPROM registers. The memoryinterfaces with the processor and saves parameters and data while thedevice is powered off. The processor and software also provide forsafety features for setting the intensity to zero when the device ispowered on and for providing a self-diagnostic mechanism. Thisself-diagnostic mechanism is preferably software driven to confirmnon-volatile parameter registration validation. The self-diagnosticoperation insures that the parameters are stored in the non-volatilememory appropriately. Any corrupted storage of the parameters results inpre-programmed power on default settings, or the statement “servicerequired” can then appear on a display panel.

Several software features interact with the compliance monitoringmechanism:

A lead monitoring feature of the device provides for monitoring of thecontinuity of at least one active channel lead at the patient pads. Theprocessor provides the open lead status for each channel while thatchannel is actively delivering a pulse, provided the intensity of pulsedelivery is above a minimum threshold level. This lead monitoringfunction enables the unique soft recovery and compliance monitoringsystems of the present invention.

The leads are sampled at selected intervals for each pulse. The softwaremonitors the leads for a feedback pulse within moments, i.e., 4microseconds, of generating the pulse. This information is stored in theprocessor. When the software of the processor detects a series ofmissing pulses, the output shuts down and the display panel displays anopen lead condition. By sampling each pulse this way the unit can run ina burst mode without being shut down by the compliance monitoringfeature. In burst mode a burst of pulses is followed by a delay beforethe next burst of pulses. This protocol prevents the unit from showingan open lead condition and shutting down as a result of the burst modedelay.

The software of the processor contains a main program polling functionthat tracks the input condition of the lead monitor input. Under normaloperating conditions the device is actively producing pulses, above adetection threshold, into a set of leads with good contact with thepatient's skin. A myriad of possible events can cause these operatingconditions to deviate from normal. For example, an electrode may loseelectrical connection with the patient's skin, or a lead may loseelectrical contact with an electrode. If the operating conditionsdeviate from the norm, it is possible for the software to take variousactions. First, it can immediately reduce the output amplitude on one orboth channels to approximately zero milliamps. The second action can beto cause the display panel to read an open channel in place of thenormal intensity display. The third action can be to start a 30 secondcount down clock for powering the unit off. The fourth action can causethe initiation of a polling pulse to look for a reconnected lead. If thelead is reconnected, the software stops the power down sequence. Thiswill then start soft recovery monitoring through software commands atthe processor.

The present invention further includes a soft recovery system designedto initiate a software routine at the processor that prevents patientsfrom being startled or injured when current flow at the at least onetreatment channel, or both channels, is resumed to the output levelpreviously set by the user/patient following a treatment disruption.Treatment disruptions can include lead disengagement at the electricalstimulation unit, electrode disengagement from the treatment site,manual user mode changes, and the like. The soft recovery systemconstantly monitors for an open lead condition. If such a condition isdetected, the output intensity to the at least one treatment probe isset to approximately zero, or a relatively negligible value of 8milliamps or less. Once the open lead condition is replaced with aclosed lead condition (i.e., the TENS unit lead is reconnected), themicroprocessor begins a ramp up stage wherein the output intensity levelis incrementally increased over a predetermined time interval toeliminate the problematic surge conditions that plague conventionalunits.

Power management is implemented into the high voltage circuit topreserve battery energy by software control performed by the processor.The software reads the programmed set output and accordingly drives thehigh voltage circuit to a target voltage level to obtain the set output.Conventional high voltage circuits are set at a fixed voltage to get themaximum available output that can be delivered. As such, the maximumvoltage setting is maintained even when an output less than the maximumoutput is required by the user. Such rigid and inconsiderateconventional techniques provide for inefficient power management as theyunnecessarily drain energy from the battery source.

The TENS unit of the present invention additionally includes a powershut off feature. Preferably, in situations where the TENS unit of thepresent invention is in an idle or waiting stage, the unit will initiatea shut down program via the microprocessor. For instance, if an openlead condition is present, and the condition has not been resolvedwithin a predetermine period of time, the software of the unit canimmediately initiate shut down to preserve power consumption. This shutdown procedure can also be initiated if the unit has waited to no availfor a user input response for a predetermined period of time, if theunit has sat idle in a state of non-use, and under like circumstances.The initiated shut down procedure can be the same as when the unit isshut off manually by the user. Examples of shut down initiators can bewhen there is an unsolved open lead condition, following a period of noinput after power up, and when a low battery condition or set treatmenttime has elapsed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a front view of an embodiment of a nerve stimulation device;

FIG. 1 b is a perspective view of an embodiment of a nerve stimulationdevice;

FIG. 2 is a back view of an embodiment of a nerve stimulation device;

FIG. 3 is a side view of an embodiment of a nerve stimulation device.

FIG. 4 a is a perspective back view of a flexible keypad for a nervestimulation device;

FIG. 4 b is a perspective top view of a flexible keypad for a nervestimulation device;

FIG. 5 a is a cross-section side view of a front panel and correspondingcomponents for a nerve stimulation device;

FIG. 5 b is a cross-section front view of a front panel andcorresponding components for a nerve stimulation device;

FIG. 6 is a plan elevation view of a lead wire male connector for anerve stimulation device;

FIG. 7 is a plan elevation view of a lead wire electrode connector for anerve stimulation device;

FIG. 8 a is a perspective view of a surface mountable multi-pinconnector for a nerve stimulation device;

FIG. 8 b is a front view of the surface mountable multi-pin connector ofFIG. 8 a;

FIG. 8 c is a side cross-section view of the surface mountable multi-pinconnector of FIG. 8 a;

FIG. 8 d is a perspective view of a multi-pin connector for a nervestimulation device;

FIG. 8 e is a front view of the multi-pin connector of FIG. 8 d;

FIG. 9 a is a block diagram of a controller and/or components for anerve stimulation device;

FIG. 9 b is a schematic diagram of selected I/O and storage componentsof a controller for a nerve stimulation device;

FIG. 9 c is a schematic diagram of an open lead monitoring circuit for anerve stimulation device;

FIG. 9 d is a schematic diagram of a power on-off switch control systemfor a nerve stimulation device;

FIG. 9 e is a schematic diagram of controller components and pulsecontrol for a nerve stimulation device;

FIG. 9 f is a schematic diagram of controller components and acommunication port for a nerve stimulation device;

FIG. 9 g is a schematic diagram of controller components and a displaycontroller for a nerve stimulation device;

FIG. 10 is a graphical representation of a strength duration curve;

FIG. 11 is a pulse diagram representing a burst pulse output mode for anerve stimulation device; and

FIG. 12 is a pulse diagram representing a special modulated pulse(“SMP”) output mode for a nerve stimulation device.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-9 e, the electrical nerve stimulation unit 10 inaccordance with the present invention generally includes a housing 12,an input panel 14, a display panel 16, a controller 18, a first channeloutput 20, a second channel output 22, and a power system 24. While thedevice 10 is generally described in terms of use as a TENS unit, it mustbe noted that other nerve stimulation applications for the device 10 areenvisioned as well.

The housing 12 generally includes a front panel 26, a back panel 28, aclip portion 38, a power access panel 44, and a battery compartment 46.The housing 12 can be of substantially oval shape and have selectedcomponents (specifically, the panels 26, 28) preferably constructed of adurable injection molded plastic material such as flame-resistantthermoplastic resins. It will be understood that other materials andshapes can be employed as well.

The front panel 26 includes a section to accept the display panel 16such that the internally mounted display 16 is visible to auser/patient. Further, the front panel 26 can include a perimeterportion 27 defined by a material change along a boundary of the ovalfront panel 26. The perimeter portion 27 can be constructed of rubber,plastic, and a myriad of other materials. The back panel 28 includes afirst lead recess 30 having a first lead aperture 34, and a second leadrecess 32 having a second lead aperture 36. The first and second leadapertures 34, 36 provide connectable communication between attachablelead wires and the internal electronic components of the device 10. Thefront panel 26 and back panel 28 are shaped and designed for abuttableattachment.

The clip portion 38 can include a belt clip 40 and an attachment member42, as shown in FIG. 3. The clip portion 38 and its correspondingcomponents 40, 42 are selectively fixed to the back panel 28 to promoteremovable convenient attachment of the device 10 to the user's person.The attachment member 42 is removably attached to the belt clip 40, withthe member 42 being connectable to the back panel 28. The attachmentmember 42 is constructed of a material having spring-like, reboundingcharacteristics, such as thin metal, wherein measurable pulling force onthe belt clip 40 by the user will permit selective attachment of thedevice to a belt, carrying case, shirt pocket, and other like regions.

The power access panel 44 is generally proximate the clip portion 38 onthe back panel 28 of the device 10, as shown in FIG. 3. The power accesspanel 44 is preferably a door panel providing selective access into thebattery compartment 46. In one embodiment, the power access panel 44includes at least two pressure tabs 45 wherein the panel 44 can bedisengaged from its locked position by applying measurable pressure onthe tabs 45. Other removably lockable devices known to one skilled inthe art can be employed as well. The battery compartment 46 is sized andshaped for operably receiving at least one battery source 48. In oneembodiment, the at least one battery source 48 is a plurality ofstandard or rechargeable AAA batteries, wherein each individual batteryis capable of holding a 1.5 volt charge. In addition, power packs, a 9volt battery, and other known battery sources can be utilized withoutdeviating from the spirit and scope of the present invention.

The input panel 14 preferably comprises a plurality of input keysdefined on a user input keypad. Referring primarily to FIG. 1 a, andFIGS. 4 a-4 b, the plurality of keys can include a power key 50, a modeselection key 52, a pulse control key 54, and a plurality of channelintensity keys 56. These channel intensity keys 56 include a channel 1intensity increase key 58, a channel 1 intensity decrease key 60, achannel 2 intensity increase key 62, and a channel 2 intensity decreasekey 64. Each of the keys for the input panel 14 are in operablecommunication with the controller 18 to control various functions andperformance characteristics of the device 10, as will be explainedherein. Each of the input panel 14 keys are preferably constructed of asilicon rubber with respective push-button control switch functionality.The power key 50 controls power toggling for the device 10 between onand off settings. The channel intensity keys 60-64 permit independentfine-tuning of the intensity output adjustments for each channel 20, 22.The pulse control key 54 enables control of the rate, cycle, pulseduration, and pulse span for applicable treatment sessions. The modeselection key 52 permits the user to select the modality of the desiredTENS treatment according to predetermined treatment goals. Preferably,each of the keys 50-64 will be recess seated within the front panel 26to enhance ease-of-use (i.e., simple key location) and to minimizeaccidental key engagement.

The display panel 16 preferably includes a Liquid Crystal Display(“LCD”) screen 70, as shown best in FIG. 1 a, and FIGS. 5 a-5 b. The LCDscreen 70 is housed behind the front panel 26 to be visibly located atthe upper portion of the front panel 26, as will be discussed hereinfurther. In one embodiment, the LCD screen 70 is a four line displayhaving eight characters per line, with each display character beingcomposed of a matrix of display dots laid out five horizontally andeight vertically. The LCD screen 70 can display alpha numericcharacters, such as those understood under ASCII standards. Outputparameters and prompting for user input are displayable on the LCDscreen 70. An LCD controller 92 operably interfaces the LCD screen 70 tothe controller 18 to provide direct line access and data communicationtherebetween, as shown in FIG. 9 g.

In one embodiment, as shown in FIGS. 4 a-4 b, the input panel 14 is aflexible pad or gasket-like structure being operably positionablebetween the abuttable front and back panels 26, 28. Namely, the inputpanel 14 is operably attachable to the controller 18 hardware platformof the device 10 on one side and sized and positioned for engagement ofthe keys 50-56 on the opposite pad side upon alignment with the frontpanel 26 key recesses. In such an embodiment, the flexible input panel14 can be made of a flexible polymer, with specified portions typicallybeing combined, injected, or extruded with a conductive material such ascarbon. In addition to the integrated keys listed herein, the flexibleinput panel 14 generally includes a LCD frame nest portion 65, at leastone seating post 67, and a seating aperture 71. The LCD frame portion 65can include a ribbon cable 69. The LCD frame portion 65 is sized andshaped to securably receive the LCD panel 70 such that the LCD panel 70is provided a resting place prior to alignment and abuttable attachmentof the front panel 26 to the back panel 28. The ribbon cable 69 permitsaccess by a data ribbon into the seated LCD 70 through the LCD nest 65to facilitate communication between the LCD 70 and the controller 18without interfering with the seating of the LCD 70. The seating posts 67provide means of engaging a corresponding portion of the controller 18.The seating posts 67 are positioned such that they will provide for aconsistent and properly aligned keypad 14 wherein connectable alignmentof the posts 67 to the controller 18 results in proper alignment of thekeys 50-56 to a corresponding at least one key switch 66. As a result,pressing of the keys 50-56 will result in an engagement with the keyswitches 66 which will be processed by the processor 74 of thecontroller 18.

Each of the keys 50-64 are in operable communication with a key switch66 that can consist of output lines and input lines to the controller18. Software monitoring of the key switch 66 for each key is performedsuch that control registers serve to identify the keys and theircorresponding activity. These register identities result in a controlmatrix to determine the current key, and the key depression status.

Referring specifically to FIGS. 9 a-9 e, the controller 18 includes atleast a processor 74, at least one open lead detect circuit 78, the LCDcontroller 92, non-volatile memory 94, and a communication port 98. Inaddition, waveform generator control circuitry can be included inoperable communication with the processor 74. The processor 74 in oneembodiment can further comprise input/output (“I/O”) controls 76 thatprovide dedicated and selectively controllable data communication linesto each of the hardware devices and circuitry within the TENS unit 10.These I/O controls can include a display line, an input panel line, apower supply line, an oscillator line, a waveform generator line, afirst channel monitoring line, and a second channel monitoring line. Theprocessor 74 can communicate with, control, and process data from eachof the interfaced controls 76.

The non-volatile memory 94 (FIG. 9 b), such as EEPROM, can be erased andreprogrammed using special software access procedures. The non-volatilememory 94 can be employed to store previous operating parameters, errorflags, critical operating parameters, device defaults, configurationflags, and a myriad of other data which is desirously maintained whilethe device 10 is powered off. The memory 94 can be selectivelyprogrammed and reprogrammed using the communication port 98, as shown inFIG. 9 f. In one embodiment, the communication port 98 is a serial dataport for receiving an external device to perform reprogramming, testing,and like operations. Other data communication interfaces known to oneskilled in the art are also envisioned for use with the presentinvention. For instance, at least one test contact point 99 can beincluded to provide for jumper type contact of a device for downloadingand uploading communication with the controller 18, and the non-volatilememory 94 in particular.

In one embodiment, the processor 74 includes at least 32 Kilobytes offlash memory for software storage and reprogramming, and 512 bytes ofRAM for a stack and to provide storage for operating parameters andvariables. Other processor 74 embodiments equipped with varyingconfigurations, such flash memory and RAM, are envisioned for use withthe present invention as well. As will be further explained herein, theprocessor 74 and its reprogrammable software enables focused controlover the operation of the hardware/circuitry platform for the device 10,as well as specific control, monitoring, and data processing for thespecific short-term and long-term treatment.

In one embodiment, the waveform generator control circuitry includes afirst channel output circuit, and a second channel output circuit, witheach output circuit corresponding to an output channel 20, 22,respectively. The output waveforms generated are typically square waves.The processor 74 interfaces with the output circuits and providesprogrammed intensity, pulse rate, and pulse width signals. Preferably,the output signals to each channel 20, 22 is driven such that the twopulses are positioned 180 degrees out of phase with respect to the otherchannel. The oscillator of the processor 74 controls the timing of thetwo pulses. In one embodiment, the waveform generator control circuitrywill include an EPOT chip 103 that will provide a programmable resistordivider allocation in 256 equal steps on each channel 20, 22 to controlthe pulse amplitude, as shown in FIGS. 9 a and 9 e. For instance, theEPOT chip 103 can be programmed to designate the pulse amplitude from 0to 127 milliamperes in 1 mA steps.

In the embodiment shown in FIG. 9 c, the open lead detect circuit 78includes a transistor 80, a resistor 82, a comparator 84, the electrodeconnector 116, 126, and an output line 88. The open lead detect circuit78 depends on the current flow out from the connector 116, 126 throughthe patient and returnable to the circuit. Upon return of the flow, thecurrent passes through the transistor 80 and then through the resistor82. This flow through the resistor 82 will generate a voltage which canbe used at the “+” input to the comparator 84. When the voltage at the“+” input to the comparator 84 exceeds the reference voltage on the “−”input to the comparator 84, a signal is sent out from the comparator 84through the output line 88 to the processor 74. It should be noted thatthis embodiment, or other lead detection circuit embodiments, can beimplemented for both channels of the device.

Referring primarily to FIGS. 6-7, and FIGS. 8 a-8 e, the first channeloutput 20 includes a first lead wire 110. In one embodiment, the firstlead wire 110 has a first lead male connector 112 at one end forremovable attachment to a first lead multi-pin connector 114 housedwithin the device 10 in the back panel 28. The multi-pin connector 114is recessed relative to the overlapping front panel 26 such that aportion of the male connector 112 is covered and protected by the frontpanel 26 to form a recessed jack when engaged. In addition, a first leadelectrode connector 116 is included at the end of the first lead wiredistal the first male connector 112. A treatment electrode is designedfor removable attachment to the first lead electrode connector 116 toreceive treatment pulses from the lead wire 110 of first channel output20. The recessed jack feature is clearly demonstrated in FIGS. 1 b and2.

Similarly, the second channel output 22 includes a second lead wire 120.In one embodiment, the second lead wire 120 has a second lead maleconnector 122 at one end for removable attachment to a second leadmulti-pin connector 124 housed within the device 10 in the back panel28. The multi-pin connector 124 is recessed relative to the overlappingfront panel 26 such that a portion of the second lead male connector 122is covered and protected by the front panel 26 to form a recessed jackwhen engaged. In addition, a second lead electrode connector 126 isincluded at the end of the second lead wire 120 distal the second leadmale connector 122. A treatment electrode is designed for removableattachment to the second lead electrode connector 126 to receivetreatment pulses from the lead wire 120 of second channel output 22.

In one embodiment, the connectors 114, 124 can be surface-mounted to thecontroller 18, i.e., a circuit board, wherein at least one member 131provides the attachment point to the controller 18. In addition, atleast one connector line 129 provides communication with the controller18, and can, in alternative embodiments, provide the attachment point tothe controller 18. FIGS. 8 a-8 e show potential embodiments for theconnectors or jacks 114, 124, while FIGS. 8 a-8 c in particular aredirected to surface-mountable connectors 114, 124. Other embodimentswith these structural characteristics and features are envisioned foruse with the present invention as well. In addition, non-surface-mountedconnectors 114, 124 or jacks can also be employed, such as those shownin FIGS. 8 d-8 e. Regardless, the connectors 114, 124 are securablyalignable with the corresponding lead apertures 34, 36 of the leadrecesses 30, 32 of the back panel 28 to form the recessed jack forprotective engagement of the lead wires 110, 120.

Each of the electrodes provide electrical conduction to thepatient's/user's skin based on output pulse signals from the outputchannels 20, 22. The electrodes are typically constructed of carbon,foil, stainless steel, or other like materials. The electrodes areinsulated and can be used with a gel material to provide adhesivecontact and even dispersion of electrical energy to skin tissue. Itshould be noted that various electrodes known to one skilled in the artcan be employed for use with the present invention.

FIG. 9 d demonstrates one embodiment of the power system 24 designed forpower off procedures at a manual switch 86 or through the control of theprocessor 74. The power system 24 generally comprises a DC power supply130 operably connected to a battery power pack 132 for providing powerto the hardware platform of the device 10, as shown in FIG. 9 a. Asstated herein, the power source for the power pack 132, and the device10, is preferably three AAA 1.5 volt batteries, or a 9.0 volt battery.In one embodiment, the power system 24 is preferably designed to complywith safety standards EN6060101, UL2601, and ANI/AAMI NS4-85requirements.

In operation, power to the device 10 is accomplished by engaging orpressing the power key 50. As stated, the controller 18 scans the keyswitch 66 for activation of any of the designated keys 50-64, such asthe power key 50. At this power up stage, the processor 74 will retrievefrom the non-volatile memory 94 any stored operating parameters.Generally, these operating parameters were stored from the most recenttreatment session and will include settings for mode, rate, width,cycle, span, and timer functions. The processor 74 can write to thenon-volatile memory 94 through dedicated I/O serial interfacestherebetween. In one embodiment, the power up initiation of the device10 will prompt the processor 74 reliability algorithms to verify thereliability of the software programs, RAM, ROM, timing, EEPROM, andother hardware and software functions.

The processor 74 will initiate a power down stage upon detectingengagement of the power key 50 during a power on period. At the powerdown stage, the processor 74 will reduce the intensity of the outputs tothe first and second output channels 20, 22 to zero and initiate a shutdown sequence. The shut down sequence, under normal circumstances, willinclude storing the operating treatment parameters such as mode, pulserate, pulse width, compliance parameters, timing parameters, and thelike, to the non-volatile memory 94. As described herein, each manual orprocessor-initiated power down can include this reference sequence ofstorage events to the non-volatile memory 94 to preserve the data duringpower off periods.

In addition, the TENS device 10 can include an automatic shut offfunction performed by the processor 74. This function will generallytrigger upon the occurrence of a timing event in conjunction with atreatment disruption or inactivity. For instance, if the processor 74detects a lead continuity break, it will initiate a timing sequence. Ifcontinuity of the lead is not re-established within the predefined timeperiod, such as 30 seconds, the power down sequence is initiated (i.e.,operating parameters are stored and the power is turned off). Otherevents can also trigger the timing sequence for shut down. For instance,failure to provide user input upon display prompting, disengagement ofthe electrode from the patient's skin, output inactivity, and a myriadof other considerations and activity can be defined as triggering eventsby the software of the processor 74.

At power up, the LCD panel 70 can display the default mode assigned bythe processor 74 according to the stored operating parameters retrievedfrom the non-volatile memory 94. There can be a plurality ofpreprogrammed TENS modes for the device 10. These modes can includenormal mode, strength duration mode, SMP mode, burst mode, ratemodulated mode, width modulated mode, and multi-modulated mode. Bypressably engaging the mode selection key 52, it is possible for theuser/patient to toggle between these modes.

To provide for electrical stimulation treatment, parameters for pulseintensity, pulse rate/cycle, and pulse duration/width parameters are setand appropriately adjusted. As will be discussed herein, the appropriateparameters can vary depending on the treatment modes selected by theuser. For instance, the intensity can be programmed to default to zerowhen the device 10 is initially powered on, with the output intensitiesof the pulses at each channel 20, 22 being independently adjustable in alinear manner from 0% to 100% in steps of 1%. In addition, the outputcan be expressed in output percentage, milliamps, volts, and the like.Other stepped interval options are also envisioned. These intervaladjustments are made at channel intensity keys 58-64.

The operational range of the pulse rate/cycle is typically between 2 and160 Hz, or pulses per second (PPS). To facilitate therapeutic paincontrol, also known as endorphin control, the adjustment can generallybe made in 2 PPS increments below 20 PPS, and 4 PPS increments above 20PPS. Upon prompting at the LCD screen 70 for a pulse rate change, keys58-64 can be utilized for adjustment, wherein the processor 74 directlycontrols the rate by regulating the time from the beginning of one pulseto the beginning of the next. The pulse width adjustment is controlledat the processor 74 by regulating the time from the beginning of a pulseto the end of that same pulse. Preferably, the pulse width is adjustablein 5 μsec increments over the operational range between 50 μsec and 400μsec (+/−2 μsec). Other incremental variations are also envisioned foruse with the present invention 10.

In one embodiment, the present invention 10 provides for an automaticpulse duration/width compensation system that maintains a fixedrelationship between the pulse duration and the output amplitude asdemonstrated in the strength duration curve of FIG. 10. When the pulseduration changes, the amplitude is adjusted automatically to follow thecurve. Preferably, this automatic compensation occurs in normal mode,burst mode, strength duration mode, or in any combination of modes. Thestrength duration curve describes the required output intensity for agiven pulse duration as defined by the following equation:

I=19.6·A/1−e ^(−0.0030593(21.338+W))

wherein I is the current in milliamps, W is the pulse duration, and A isan intensity factor from 0% to 100% intensity. As stated, the pulseduration is generally adjustable between 50 μsec and 400 μsec. Thisduration is adjustable through user depression of the pulse control key54 followed by the appropriate channel intensity keys 56. Cycle timeadjustments can be made by pressing the pulse control key 54momentarily. The pulse cycle time is typically adjustable in 0.5 secondincrements from 0.5 seconds to 12 seconds.

The various preferred modes available for stimulation treatment usingthe present invention are described below.

Normal mode: The normal mode setting defines a constant output at aselected pulse width and pulse rate to the output channels 20, 22. Theuser can generally adjust the pulse rate between 2 and 160 Hz, orbetween other selected rate values. The pulse width is generallyadjustable between 50 and 400 μsec. Both output channels 20, 22 aredriven with pulse waveforms that are based upon the same rate and widthsettings. The pulse on the second channel output 22 will be 180 degreesout of phase with that generated on the first channel output 20.

Strength duration mode: the strength duration mode is applied to the twochannels 20, 22 in a modulated manner over a selectable cycle time thatis variable from 0.5 to 12 seconds. During said cycle, the pulse rate ispreferably fixed at 100 PPS with the nominal pulse width set at 225μsec. A modulation range percentage from 0% to 100% is available to thepatient, with this range specifying the amount of pulse width modulationdeviation from the nominal width over the selected cycle time. The pulseamplitude and pulse duration are varied inversely to match the strengthduration curve. At 100%, the modulation will cycle up and down theentire range of pulse duration from 50 μsec to 400 μsec. At 0%, themodulation will cease entirely since the pulse duration will be fixed at225 μsec.

Burst mode: in burst mode, as shown in FIG. 11, the user selects thepulse rate over the selectable range form 16 PPS to 160 PPS during theburst, in 2 Hz increments. The output signal intensity is adjustablebetween 0% to 100%. Rate thresholds are imposed such that a pulse ratebelow 16 PPS is not permitted, and the pulse width is fixed. Therepetition rate can occur at approximately a 2 Hz rate —one burst pereach ½ second interval, or at other designated values/rates.

SMP mode: the SMP mode inversely correlates the pulse rate/cycle and thepulse duration/width modulate such that when the pulse rate increases,the pulse duration decreases. This correlation creates inverse andsymmetric pulse phases for the output channels 20, 22, as demonstratedin FIG. 12. The pulse rate will generally modulate non-linearly from theset rate down to 2 PPS in a 12 second cycle, with the rate staying inthe 2 PPS to 10 PPS range for ⅓ of the cycle time. Increases ordecreases in this correlation are made by incrementally depressing thechannel increase/decrease keys 58-64. Generally, the pulse rate range is20 PPS to 125 PPS, and the pulse duration/width range is 50 μsec to 400μsec.

Rate modulate mode: in rate modulate mode, the output signal isdelivered with modulated pulse rates. The adjustable pulse width isconstant over the normal available ranges, wherein the pulse ratemodulates can be between the set rate and 66% of the set rate every 2.5seconds, or other selected values. These values are adjustable with thecorresponding keys 54, 56, with the pulse rate being selectable between2 to 100 Hz (PPS), or other selected values.

Width modulated mode: width modulated mode controls the pulse width toalternate between the selected value and 50% of the selected value every2.5 seconds, or other selected values. The pulse rate is selectablewithin the available normal range. The pulse duration is selectablebetween 50 μsec to 300 μsec. The pulse rate can be selectable between 2to 125 Hz (PPS), or other selected values.

Multi-modulated mode: In the multi-modulated mode, the output isdelivered with modulated pulse rate and pulse width such that both thewidth and rate modulate inversely to each other, and the cycle period isadjustable. The pulse width typically decreases to 50% of the set valuewith a 40 μsec minimum. The pulse rate when set to 100 Hz modulates to66% of the 100 Hz, or some selected value.

Mode selection depends greatly on the particular needs and treatmentgoals for the user/patient. By adjusting the above-described controlsand treatment variables at the input panel 14 based on prescribedtreatment and/or prompting on the display panel 16, a treatment sessionis initiated and monitored. One important monitoring function performedby the present invention is the open lead monitoring system.

The open lead monitoring system allows the device 10 to detect an openor circuit condition at either or both of the channel outputs 20, 22.For instance, if a lead wire 110, 120 is disconnected from the channeloutputs 20, 22, an open condition will be detected by the processor 74and a preprogrammed series of steps will be initiated. At the time ofdetection, the processor 74 will immediately initiate an adjustment tothe output channel 20, 22 such that the output signal is brought down toapproximately zero. At the time of output reduction, a warning messagemay be displayed on the LCD screen 70. The monitoring is facilitated bya periodic polling test pulse to the channels 20, 22 such that leadcontinuity is monitored within 4 μsec after the generation of a pulse.If a return signal is not received, the open circuit condition isassumed. If a return signal is received, then the soft recovery functionoccurs.

In one embodiment, a low battery monitoring system is also in place withthe device 10 during operation. With such a system, stepped indicatorsare processed to provide more detailed analysis of the level of batteryvoltage reduction that is occurring with the device 10. For instance, ifthree AAA (1.5 volt) batteries are being used, a total of 4.5 volts willbe available at peak power. One embodiment of the present invention willmonitor the voltage at the power system 24 at threshold levels of 3.2volts, 2.7-3.2 volts, and less than 2.7 volts. While other thresholdsand monitoring embodiments are obviously envisioned, these thresholdsprovide a good explanation of how the monitoring system works. When thebattery input level reaches 3.2 volts, the unit will display a lowbattery indication at the LCD screen 70. When the battery voltage dropsto the second threshold level of approximately 2.7 to 3.0 volts, alloutput will cease and the channel indicators will go off, with only thelow battery indicator showing on the LCD screen 70. Preferably, at thenext threshold level below approximately 2.7 volts, all power to theunit 10 will cease, including low power indications on the LCD screen70. Obviously, other permutations on the threshold examples andmonitoring are envisioned and can be implemented without deviating fromthe spirit and scope of the present invention. As indicated herein forother shut down sequences, the processor 74 will store parameter data(i.e., mode data, compliance data, pulse data, etc.) to the non-volatilememory 94 as part of the shut down sequence before power to the deviceis substantially set to zero.

Open Lead Monitoring

As further described herein for the open lead detect circuit 78 of FIG.9 c, the device 10 performs a lead continuity monitoring function thatevaluates or polls the output pulse delivery, such as current, for atreatment application. It should be noted that this pulse delivery isthe key monitoring event rather than mere pulse generation, which maynever reach the patient due to a disruption. Treatment disruptions caninclude lead 110, 120 disengagement at the connectors 114, 124, poorelectrode skin contact, mode changes, and the like. If such conditionsare detected, the output intensity to the output channels 20, 22 isimmediately set to approximately zero, or a relatively negligiblecurrent of approximately 8 milliamps or less. The levels stay at the lowpolling current level until the disruption is eliminated. The lowpolling current signal can include a single 50 μsec polling pulse, ataround 5-8 milliamps, delivered to the channels 20, 22 twice a second,wherein the processor 74 monitors for a return signal. Once thedisruption is eliminated, i.e., a closed lead condition is establisheddue to the reconnection of the leads 110, 120, feedback from the pollingpulse signals the processor 74, which correspondingly starts a ramp upstage which is further described herein. This disruption signal canrepresent no output current. When an open channel exists for either thefirst channel 20 or second channel 22, the processor 74 indicates theopen channel condition on the display panel 16. The polling featureensures a soft recovery that will not startle the patient when the openchannel condition is corrected, and further facilitates the patientcompliance monitoring system.

Compliance Monitoring

The invention accomplishes compliance monitoring by storing a number ofparameters in the non-volatile memory 94 which can include EEPROMregisters. As indicated, the open lead monitoring system enhances theaccuracy of measuring true patient compliance. An open lead conditionresulting in the low polling current levels equates to a non-compliantperiod. As such, accurate compliance monitoring is achieved wherein thedevice 10 does not count open lead periods as valid therapy periods.With such a mechanism, conditions such as disconnected electrodes andleads disrupt the output, resulting in a non-compliant open lead period.Conventional devices have monitored compliance merely according topower-on periods or output generation. With the present invention, animportant distinction is made between the output generated and theoutput actually delivered to the patient's skin. The open lead conditionmonitoring makes this distinction possible as the processor 74 iscontinuously monitoring whether the output signal is delivered ordisrupted, and when a disruption, or open lead condition, is removed.

In addition, the TENS device 10 allows for serial number storage, whichcan include an eight-bite serial number (ASCII characters), or otherselected parameters. The serial numbers are stored within the first fourlocations of the memory 94. Each device 10 has a unique serial numberthat provides for traceability to the date of manufacture. The device 10also includes device timer storage wherein the timers can include thepatient usage timer, the device usage timer, and independent modal usagetimers. The timer values will be stored within an appropriate number oflocations within the memory 94.

In one embodiment, a plurality of time accumulators can be implementedto achieve compliance monitoring. First, the processor 74 softwareaccumulates the active time during which the device 10 is deliveringpulses to the patient. The time can be stored on a resolution ofminutes. For instance, the accumulator can accumulate time for up to65,000 hours which is equivalent to over seven years of operating time.The device active time accumulator is preferably stored in thenon-volatile memory 94, wherein each timer can occupy three bits. Thetimer value can be stored once every ten minutes, or whenever the deviceis shutdown. The time accumulator is available to the prescribingpractitioner for reading and clearing through use of the communicationport 98.

The processor 74 software can also make available mode usage timeaccumulators that accumulate the active time in which the device 10 isdelivering pulses in each of the operating modes. The times areaccumulated into separate accumulators, are designed to accumulate timefor up to 65,000 hours, and are preferably stored in the non-volatilememory 94 as well. Again, the timer values are stored once every tenminutes or upon shutdown of the device 10, and are available for readingand clearing through the use of the communication port 98.

A patient usage timer can be included to accumulate the active timeduring which the device 10 is delivering pulses irrespective of mode ofoperation. The time is accumulated into a time accumulator as aresolution of minutes, is preferably timed to accumulate time for up to65,000 hours, and is also stored into the non-volatile memory 94. Again,the timer value is stored, preferably, every ten minutes and upon shutdown. The patient usage timer is available for display on the LCD screen70 and may be reset through the communication port 98.

The device 10 can also include a therapy timer. The therapy timerpermits the unit to turn itself off automatically after the expirationof a programmable duration timer. This time is preferably updated/storedin the memory 94 as an operating parameter value. The duration timer ispreferably programmable in steps of five minutes up to a maximum ofeight hours. Other timing periods and intervals are also envisioned foruse with the device 10 of the present invention. Whenever the device 10starts delivering pulses with any amplitude approximately over 5milliamps, the software starts a countdown using the processor 74 timingbased on the setting of the therapy timer parameter. Other relativelylow pulses, such as those below 8 milliamps, can be implemented as well.As such, the open lead detection/monitoring described herein affects theinitiation of the actual countdown. An open lead condition will halt thecountdown such that only actual pulse delivery times result in a timecountdown. When the countdown timing expires, the device 10 initiatesthe power down sequence as the therapy duration is considered complete.

High Voltage Level Control System

As described herein, the device 10 of the present invention can providepower level indications and monitoring of low battery power atpredetermined thresholds. In addition, a system of efficiently managingthe consumption of power for the device 10 is also implemented.Specifically, a high voltage level control system is included whichprovides variable excitation of the generator control circuitry.

The high voltage level control system promotes variable control over thegenerator circuitry by permitting the generator to operate at a variablerange controlled by the software of the processor 74 so that the outputcan be generated to the desired output amplitude. This prolongs batterylife by avoiding running the high voltage system at the maximum levelwhen the device 10 is operating at less than maximum output. Thegenerator output can be variably controlled or fine-tuned by theprocessor 74 software. The software drives the processor 74 topreferably produce a pulse width modulated signal that varies from 0% to100% duty cycle and correspondingly produces the desired range of highvoltage level control. As a result, intelligent high voltage levels arepromoted and inconsiderate operation of the generator circuitry isavoided.

The processor 74 employs the high voltage level control system of thepresent invention by monitoring the exact level of available voltagerequired at the high voltage circuit to achieve the set output level. Assuch, it is possible to minimize any overcharging of the high voltagecircuit, and to consequently promote power conservation. The processor74 is programmed to monitor and adjust high voltage to achieve therequired output. For instance, an embodiment designed to operate withthree battery sources (i.e., 3 AAA batteries), each having 1.5 volts, ora combined voltage of 4.5 volts, which provides power to the highvoltage circuit, operates most efficiently when only the necessarysufficient power is provided to deliver the set output. If it isdetermined that 40 volts is needed, then overcharging above that levelrequired to obtain that will be avoided, and that ideal voltage will besubstantially maintained in the high voltage circuit. The processor 74knows what the output is set at and only charges the capacitor in thehigh voltage circuit to the ideal level to produce that set output. Forinstance, the capacitor in the high voltage circuit must be set to acertain level in order for the high voltage circuit to meet the requiredoutput. The processor 74 will determine the pulses to charge thecapacitor to obtain this level, and will monitor and maintain the ideallevel. For example, if the set output is 50% for the high voltagecircuit, there is no need to charge the capacitor to a level required tooutput 100% intensity. Overcharging is an innate problem withconventional devices that causes unnecessary drainage on batteries. Withthe present invention, when the device 10 uses a portion, or pulse, fromthe capacitor, the processor 74 periodically ensures that a replacementpulse(s) is directed to substantially maintain the capacitor at ideallevels.

Soft Recovery

The TENS device 10 further includes a soft recovery system designed toinitiate a software routine at the processor 74 that preventsusers/patients from being startled or injured when current flow at theelectrodes are resumed following a treatment disruption. Treatmentdisruptions can include lead 110, 120 disengagement at the connectors114, 124, poor electrode skin contact, mode changes, and the like. Ifsuch conditions are detected, the output intensity to the outputchannels 20, 22 is immediately set to approximately zero, or arelatively negligible current of approximately 8 milliamps or less. Thelevels stay at the low polling current level until the disruption iseliminated. Once the disruption is eliminated, i.e., a closed leadcondition is established due to the reconnection of the leads 110, 120,feedback from the polling pulse signals the processor 74, which sets theoutput intensity to zero and then correspondingly starts a ramp upstage. In the ramp up stage the output intensity level is incrementallyincreased over a predetermined time interval to eliminate theproblematic surge conditions that plague conventional units. In oneembodiment, elimination of the open circuit flag at the processor 74will cause a step up feature that permits the output amplitude at thechannels 20, 22 to increase from approximately zero to the programmed orset level over a period of approximately 2.55 seconds. The low pollingcurrent signal can include a single 50 μsec polling pulse, at around 5-8milliamps, delivered to the channels 20, 22 twice a second, wherein theprocessor 74 monitors for a return signal. When a return signal isdetected, the described soft ramp up is performed. Preferably, the softrecovery protection is triggered when there has been a disconnection ofthe first lead wire 110 and/or the second lead wire 120, or when therehas been a user-initiated mode change during an active treatmentsession. However, the mode change initiation of the soft recovery can beperformed by the processor 74 software upon a change in the mode anddoes not require an open lead condition event. Whether this mode changeis intentional or unintentional, it must be properly addressed toeliminate discomfort to the user from undesirable amplitude spikes.

Those skilled in the art will appreciate that other embodiments inaddition to the ones described herein are indicated to be within thescope and breadth of the present application. Accordingly, the applicantintends to be limited only by the claims appended hereto.

1-26. (canceled)
 27. An electrical nerve stimulation device, comprising:a display screen; and a housing having a front panel portion; a backpanel portion attachable to the front panel portion; and a keypad panelintermediately positionable between the front panel and the secondpanel, the keypad panel having a display screen frame nest adapted tosecurely receive the display screen to facilitate alignment of thedisplay screen within the housing.
 28. The device of claim 27, whereinthe display screen is a Liquid Crystal Display (LCD).
 29. The device ofclaim 27, wherein the keypad panel is constructed of a flexiblematerial.
 30. The device of claim 29, wherein at least one of theflexible materials is selected from a group consisting of: polymers, andpolymers containing carbon.
 31. The device of claim 27, wherein thekeypad panel includes a plurality of keys positioned on the keypad panelfor alignment with corresponding apertures in the front panel.
 32. Anelectrical nerve stimulation device, comprising: display means forproviding visual display to a user during operation of the device; and ahousing having a front panel portion; a back panel portion attachable tothe front panel portion; and panel means intermediately positionablebetween the front panel and the second panel for securely nesting thedisplay screen to facilitate alignment of the display screen within thehousing.
 33. The device of claim 32, wherein the panel means isconstructed of a flexible material.